QUB-3005, a bioactive peptide from the defensive skin secretion of Rana amurensis

In the latter class of molecules, a large number of peptide antibiotics has been isolated and characterised from different amphibian species. Particularly, antimicrobial peptides (AMPs) are considered as excellent candidates for development of novel drugs for antibiotic therapy, as they normally have a wide range of activities, for example, by disrupting the phospholipid bilayer of the target cell membrane to kill bacteria or inhibit their growth.<br><br>In this thesis, a bioactive peptide, named QUB-3005, was isolated using “shotgun” cloning of its biosynthetic precursor-encoding cDNA from a skin secretion-derived cDNA library of Rana amurensis.

The primary structure of this peptide was confirmed based on experiments of cloning and online BLAST alignment analysis. Then, solid-phase synthesis methodology was used to chemically-synthesise the peptide, and the molecular mass of this peptide was identified by MALDI-TOF mass spectrometry. After that, RP-HPLC was employed for purification purposes and then the bioactivities of this peptide were examined by antimicrobial assays, haemolytic assays and anticancer cell assays.<br>The data indicated that the QUB-3005 inhibited the growth of E. coli, P. aeruginosa, S. aureus and C. albicans in antimicrobial assays but showed a relatively high haemolytic activity.